Nutritive and photosynthetic ecology of subsurface chlorophyll maxima in Canadian Arctic waters

[摘要] Assessments of carbon and nitrogen (N) assimilation inCanadian Arctic waters confirmed the large contribution of subsurfacechlorophyll maxima (SCM) to total water-column production from spring tolate fall. Although SCM communities showed acclimation to low irradiance andgreater nitrate (NO₃⁻) availability, their productivity wasgenerally constrained by light and temperature. During spring–early summer,most of the primary production at the SCM was sustained by NO₃⁻,with an average f-ratio (i.e., relative contribution of NO₃⁻ uptaketo total N uptake) of 0.74 ± 0.26. The seasonal decrease inNO₃⁻ availability and irradiance, coupled to the build up ofammonium (NH₄⁺), favoured a transition toward a predominantlyregenerative system (f-ratio = 0.37 ± 0.20) duringlate summer and fall. Results emphasize the need to adequately consider SCMwhen estimating primary production and to revisit ecosystem modelparameters in highly stratified Arctic waters.

[学科分类] 地球化学与岩石